1. Field of the Invention
The present invention relates to an apparatus and a process for supplying gas, more specifically to an apparatus and a process for selecting any one of a plurality of gases and then supplying them to an instrument, in particular a trace impurity analyzer such as an atmospheric-pressure ionization mass spectrometer (APIMS).
2. Description of Prior Art
Recently, in the field of gas analysis, it is increasingly important to consecutively and rapidly analyze a plurality of sample gases, using a same analyzer. For this purpose, a gas passage switching means such as in the Japanese laid-open publication Hei No. 10-122498, has been used for switching a sample gas to be supplied to a gas analyzer.
However, in the case of switching sample gas by opening and closing a plurality of valves, the gas could stagnate inside the valves or inside the pipings of the vicinity of the valves, and in the case of switching the kind of gas, a different kind of gas could be mixed with the sample gas. As a different kind of gas mixed with the sample gas becomes an impurity component with respect to the sample gas, in particular in the case of analyzing trace impurities present in high-purity gas using a high-sensitivity gas analyzer such as an atmospheric-pressure ionization mass spectrometer (APIMS) or the like, different kinds of gases mixed therein could greatly affect the analysis results, with only a small quantity. Furthermore, if the sample gas reacts to the gas mixed therein, as in the case of hydrogen and oxygen, there is an undesirable possibility that both gases react each other and explode.
For this reason, in the previous gas analyzer, a purge gas is subject to flow in order to completely remove the sample gas of the previous step whenever sample gas is analyzed. However, the above operation requires a long time, and thus a plurality of sample gases could not be analyzed in a short time. In addition, in the case of using a plurality of valves, if two or more valves become in the opening state simultaneously, owing to some trouble in the valves, not only the analysis experiences trouble, but also the gases could undesirably react to one another. Moreover, in such cases, as the operation of the analyzer should be stopped for exchanging the broken-down valves, it took a very long time to reinitiate the operation.
The present invention aims to provide with an apparatus and a process for supplying gas capable of rapidly switching the gas to be supplied to an instrument and preventing reactive gases from mixing one another.
To achieve the object, a gas supplying apparatus according to the present invention comprises: a 4-way block valve which is a main switching valve, having two inflow ports and two outflow ports; an instrument connection passage connected to an instrument, such as an analyzer, to which the one of the two outflow ports is connected; an exhaust passage to which the other of the two outflow ports is connected; common gas supplying passages respectively connected to the two inflow ports of the 4-way block valve; a switching valve(s) made of a 2-connected 3-way block valve(s) or a 4-way block valve(s) connected to the at least one of the two common gas supplying passages; and two gas supplying passages switchably connected to the 2-connected 3-way block valve(s) or the 4-way block valve(s).
Furthermore, the 2-connected 3-way block valve(s) of the switching valve(s) comprises: an outflow port connected to the common gas supplying passage; and first and second inflow ports connected to the two gas supplying passages respectively; and the 4-way block valve(s) of the switching valve(s) comprises: first and second outflow ports wherein the first outflow port is connected to the common gas supplying passage and the second outflow port is connected to the exhaust passage; and first and second inflow ports connected to the two gas supplying passages respectively.
Furthermore, the 2-connected 3-way block valve(s) of the switching valve(s) comprises: first and second inflow ports; an outflow port; first valve for switching the first inflow port and the outflow port between a communicating state and a blocking state and second valve for switching the second inflow port and the outflow port between the communicating state and the blocking state; wherein the first and the second valves are operated in such a way that when the one of the first and the second valves is brought into the communicating state, the other of the first and the second valves is brought into the blocking state. An exhaust passage with a flow rate regulator is branch-connected in a flow passage communicating with the first inflow port.
On the other hand, the 4-way block valve(s) of the switching valve(s) comprises: first and second inflow ports; first and second outflow ports; first valve for switching the first inflow port and the first outflow port between a communicating state and a blocking state; second valve for switching the second inflow port and the first outflow port between the communicating state and the blocking state; third valve for switching the first inflow port and the second outflow port between the communicating state and the blocking state; fourth valve for switching the second inflow port and the second outflow port between the communicating state and the blocking state; and an exhaust passage with a flow rate regulator connected to the second outflow port wherein the valves are operated in such a way that when the first valve and the fourth valve are brought into a communicating state, the second valve and the third valve are brought into a blocking state and when the first valve and the fourth valve are brought into the blocking state, the second valve and the third valve are brought into the communicating state.
Furthermore, a process of the present invention for supplying gas by using the above-mentioned gas supplying apparatus, comprises the steps of: providing each of the two common gas supplying passages with the first and the second switching valves respectively, in the case that two kinds of gases which react to each other when mixed, are present in a plurality of gases to be supplied to the respective gas supplying passages; connecting a passage for supplying first reactive gas and a passage for supplying first non-reactive gas to the first switching valves and connecting a passage for supplying second reactive gas and a passage for supplying second non-reactive gas to the second switching valve; supplying the second non-reactive gas from the second switching valve to the main switching valve, in the case of supplying the first reactive gas to the instrument from the first switching valve via the main switching valve; switching the first switching valve supplying the first reactive gas in order to supply the first non-reactive gas, in the case of switching the gas to be supplied to the instrument to the gas coming from the first switching valve; and switching the main switching valve such that the gas to be supplied to the instrument is switched to the gas coming from the first switching valve after the concentration of the first reactive gas present in the gas to be supplied to the apparatus is lowered below a predetermined concentration.